Plasma-utilizing processing apparatuses, the most typical of which is an etching apparatus, have been widely applied to a semiconductor producing process or a liquid crystal display's board producing process.
As one example of the plasma-utilizing processing apparatuses, there exists a parallel-plate type plasma etching apparatus illustrated in FIG. 26. In this type of apparatus, as illustrated in FIG. 26, the etching is performed as follows: An output voltage from a power amplifier 84 is modulated using a high-frequency signal from a signal generator 83. Next, the resultant high-frequency voltage is distributed by a distributor 85, then being applied between an upper electrode 81 and a lower electrode 82 which are located in parallel to each other inside a processing chamber. Moreover, the electrical discharge between both of the electrodes 81, 82 generates plasma 71 from an etching gas. Finally, a to-be-processed target, e.g., a semiconductor board (i.e., wafer), is etched by radicals of the plasma. As the high-frequency signal, there is employed a frequency of an order of, e.g., 400 kHz.
In the above-described plasma etching apparatus, there has been known the following fact: Reaction products produced as the result of the etching reaction by the plasma processing are deposited on the wall surface of the plasma processing chamber or on the electrodes. Then, the deposited products are flaked off with a lapse of time, thereby becoming floating particles. At the moment that the etching processing is over and the plasma discharge has been stopped, the floating particles drop down on the wafer, becoming the matters adhering thereto. The adhering matters give rise to a defect in the circuit characteristic or a defect in the circuit pattern's outside appearance, eventually becoming a cause of a decrease in the yield or a reduction in the reliability of the circuit components.
As apparatuses for inspecting the above-described particles that have adhered to the wafer surface, a lot of apparatuses have been reported and developed to practical use. In these apparatuses, however, the inspection is performed once the wafer has been extracted from the plasma processing apparatus. Accordingly, at a point in time when it was recognized that a large number of particles had been generated, another processing for the wafer had been already going on. This situation results in a problem of the decrease in the yield caused by the occurrence of a large number of defects. Also, in the estimation after the processing, it is impossible to determine the distribution and the time-elapsed variation of the generation of the particles inside the processing chamber.
Consequently, in the field of the semiconductor production and the liquid crystal display production, there exists a demand for a technology that allows an in-situ and real-time monitoring of the contamination situation inside the processing chamber.
The size of the particles floating inside the processing chamber is in the range of submicron to hundreds of μm. However, in the semiconductor production field where the higher integration is increasingly developing to a 256-Mbit DRAM (i.e., Dynamic Random Access Memory) and further up to a 1-Gbit DRAM, the minimum line-width of the circuit pattern is now becoming more and more microminiaturized, i.e., 0.25 μm to 0.18 μm. As a result, the size of the particles to be detected is also required to be of the submicron order.
As the prior arts for monitoring the particles floating inside the processing chamber (the vacuum processing chamber) such as the plasma processing chamber, the technologies disclosed in the following applications can be cited: JP-A-57-118630 (i.e., prior art 1), JP-A-3-25355 (i.e., prior art 2), JP-A-3-147317 (i.e., prior art 3), JP-A-6-82358 (i.e., prior art 4), JP-A-6-124902 (i.e., prior art 5), and JP-A-10-213539 (i.e., prior art 6).
In the above-described prior art 1, there is disclosed an evaporating apparatus including a member for irradiating a reaction space with a parallel light that has a spectrum differing from a spectrum of a self light-emitting light in the reaction space, and a member for detecting scattered-lights from microscopic particles generated in the reaction space as a result of receiving the irradiation with the parallel light.
Also, in the above-described prior art 2, there is disclosed a microscopic particle measuring apparatus for utilizing a scattering by a laser light so as to measure microscopic particles adhering to a semiconductor apparatus's board surface and floating microscopic particles, the microscopic particle measuring apparatus including a laser light phase modulating unit for generating two laser lights having an equal wavelength, having a phase difference therebetween, and modulated with a predetermined frequency, an optical system for causing the two laser lights to intersect to each other in a space containing the microscopic particles that are targets to be measured, a light detecting unit for receiving lights so as to convert the lights into electrical signals, the lights being obtained by scattering by the microscopic particles that are targets to be measured, and a signal processing unit for extracting, from among the electrical signals based on the scattered-lights, an electrical signal component the frequency of which is equal to or two times as large as the frequency of a phase modulating signal in the laser light phase modulating unit and the phase difference of which with the phase modulating signal is fixed in time.
Also, in the above-described prior art 3, there is described a technology including a step of performing a scanning irradiation with a coherent light so as to cause lights to be generated in situ, the lights being scattered inside a reaction container, and a step of detecting the lights scattered inside the reaction container, whereby the scatted lights are analyzed thereby measuring a contamination situation inside the reaction container.
Also, in the above-described prior art 4, there is described a particle detector including a laser member for generating a laser light, a scanner member for scanning, using the laser light, a region inside a reaction chamber of a plasma processing tool containing particles to be observed, a video camera for generating video signals of the laser lights scattered by the particles inside the region, and a member for processing and displaying an image of the video signals.
Also, in the above-described prior art 5, there is described a plasma processing apparatus including a camera apparatus for observing a plasma generating region inside a plasma processing chamber, a data processing unit for processing an image so as to obtain target information, the image being obtained by the camera apparatus, and a control unit for controlling at least one of an exhausting member, a process-gas introducing member, a high-frequency voltage applying member, and a purge-gas introducing member in accordance with the information obtained in the data processing unit so that the particles will be decreased.
Also, in the above-described prior art 6, there is described a microscopic particle censor including a light sending-out device for sending out a light beam with which a measurement volume is irradiated in a manner of being cut across, a detector, and the optical system that converges the scattered-lights from the measurement volume and directs the converged lights toward the light detector, the detector being configured so that the light detector generates a signal for indicating an intensity of the light directed toward the light detector, and a signal processing member including pulse detectors and an event detector, the pulse detectors connected to each other so that the pulse detectors analyze the signal from the light detector and detecting pulses within the signal from the light detector, the event detector corresponding to a microscopic particle and specifying a series of pulses caused by scattered-lights, the scattered-lights by the microscopic particle being associated with a plurality of irradiations with the light beam which are performed while the microscopic particle is moving within the measurement volume.
In the above-described respective prior arts, the irradiation with the laser light is performed from an observing window provided on a side wall of the plasma processing apparatus, and then a forward scattered laser light or a side scattered laser light is detected from an observing window that is provided on an opposed side wall or the other side wall and that differs from the above-described laser-irradiating observing window. Accordingly, in this method of detecting the forward scattered-light or the side scattered-light, the irradiating optical system and the detecting optical system are formed in different units each. Moreover, there is a need of providing the two observing windows on which these systems are mounted. Also, the optical-axis adjustment or the like must be made in either of the irradiating optical system and the detecting optical system. This has made the handling troublesome and complicated.
Also, the observing windows on the side wall of the processing chamber such as the plasma processing chamber are usually provided on almost all types of the processing apparatuses in order to monitor the plasma emitted-light and so on. In not a few cases, however, only one observing window is provided thereon. Consequently, there exists a problem that the conventional methods necessitating the two observing windows is inapplicable to the producing apparatuses having the processing chamber equipped with the only one observing window.
Furthermore, in the conventional methods of detecting the forward scattered-light or the side scattered-light, when trying to observe the particles-generated situation all over the entire surface of the to-be-processed target such as the wafer by performing a rotation scanning of the processing chamber-irradiating irradiation beam, many of the observing windows and the detecting optical systems become required. This condition becomes a cause of a tremendous amount of cost-up. In addition to this, providing many of the observing windows and the detecting optical systems is, actually, very difficult from the restriction on the space factor.
Meanwhile, in the semiconductor production field where the higher integration is increasingly developing to the 256-Mbit DRAM and further up to the 1-Gbit DRAM, the minimum line-width of the circuit pattern is now becoming more and more microminiaturized, i.e., 0.25 μm to 0.18 μm. As a result, the size of the particles to be detected is also required to be of the submicron order. In the prior arts, however, it is difficult to separate the particle scattered-lights from the plasma emitted-light. This condition limits the application of the prior arts into the observation of comparatively large particles, thereby making it difficult to detect the microscopic particles of the submicron order.